Display device with encapsulation layer with varying ratios of carbon to silicon and oxygen to silicon and method of fabricating the same

ABSTRACT

A display device includes a organic light emitting device and an encapsulation structure disposed on the organic light emitting device that seals the organic light emitting device. The encapsulation structure includes a first inorganic encapsulation layer disposed on the organic light emitting device, an organic layer disposed on the first inorganic encapsulation layer, and a second inorganic encapsulation layer disposed on the organic layer. The organic layer includes a first organic layer disposed on the first inorganic encapsulation layer and a second organic layer disposed on the first organic layer. An atomic ratio of carbon to silicon in the first organic layer is less than an atomic ratio of carbon to silicon in the second organic layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application is a divisional of U.S.application Ser. No. 15/846,015, filed on Dec. 18, 2017 in the U.S.Patent and Trademark Office, which claims priority under 35 U.S.C. § 119from, and the benefit of, Korean Patent Application No, 10-2017-0043117,filed on Apr. 3, 2017 in the Korean Intellectual Property Office, thecontents of both of which are herein incorporated by reference in theirentireties.

BACKGROUND

Embodiments of the present disclosure are directed, to a display deviceand a method of fabricating the same, and in particular, to a displaydevice that can prevent interfacial separation between elements and hasimproved reliability, and a method of fabricating the same.

An organic light emitting display device includes an organic lightemitting device which is composed of an anode, an organic light emittinglayer, and a cathode. An organic light entitling layer is vulnerable tomoisture or oxygen. In detail, if external moisture or oxygeninfiltrates into an organic light emitting display device, the lightemitting layer may deteriorate, and thus, various defects, such as darkspots or pixel shrinkage, can occur. Accordingly, am encapsulationstructure is used to protect an organic light emitting device fromexternal moisture or oxygen.

SUMMARY

Some embodiments of the inventive concept provide a display device thatcan prevent extraneous material, such as oxygen or moisture, frominfiltrating therein and thereby to have improved reliability.

Some embodiments of the in entire concept provide a method offabricating a display device, including forming layers of anencapsulation structure through a continuous process to allow the layersto have improved adhesive characteristics.

According to some embodiments of the inventive concept, a display deviceincludes an organic light emitting device and an encapsulation structuredisposed on the organic light emitting device that seals the organic,light emitting device. The encapsulation structure includes a firstinorganic encapsulation layer disposed on the organic light emittingdevice, a first organic layer disposed on the first inorganicencapsulation layer and a second organic layer disposed on the firstorganic layer, and a second inorganic encapsulation layer disposed onthe second organic layer atomic ratio of carbon to silicon in the firstorganic layer is less than an atomic ratio of carbon to silicon in thesecond organic layer.

In some embodiments, the atomic ratio of carbon to silicon in the firstorganic layer is less than 1.24, and the atomic ratio of carbon tosilicon in the second organic layer is greater than 1.24.

In some embodiments, the atomic ratio of carbon to silicon in the firstorganic layer ranges from 1.20 to 1.24, and the atomic ratio of carbonto silicon in the second organic layer ranges from 1.24 to 1.30.

In some embodiments, the first and second organic layers include asilicone-based compound that includes silicon-oxygen chains.

In some embodiments, an atomic ratio of oxygen to silicon in the firstorganic layer is greater than an atomic, ratio of oxygen to silicon inthe second organic layer.

In some embodiments, the atomic ratio of oxygen to silicon in the firstorganic layer is greater than 0.62, and the atomic ratio of oxygen tosilicon in the second organic layer is less than 0.62.

In some embodiments, the atomic ratio of oxygen to silicon in the firstorganic layer ranges from 0.62 to 0.64, and the atomic ratio of oxyoxygen to silicon in the second organic layer ranges from 0.60 to 0.62.

In some embodiments, the display device further includes an intermediateorganic layer disposed between the first organic layer and the secondorganic layer, an atomic ratio of oxygen to silicon in the intermediateorganic layer may have a value between those in the first organic layerand the second organic layer.

In some embodiments, the atomic ratio of carbon to silicon in the firstorganic layer increases with decreasing distance from the second organiclayer.

In some embodiments, the atop is ratio of oxygen to silicon in the firstorganic layer increases with decreasing distance from the firstinorganic encapsulation layer.

According to some embodiments of the inventive concept, a display deviceincludes an organic light emitting device, a first inorganic layerdisposed on the organic light emitting device, a first organic layerdisposed directly on the first inorganic layer, a second organic layerdisposed directly on the first organic layer, and a second inorganiclayer disposed directly on the second organic layer. An atomic ratio ofcarbon to silicon in the first organic layer is less than an atomicratio of carbon to silicon in the second organic layer.

In some embodiments, the first and second organic layers each include asilicone-based compound that includes silicon-oxygen chains, and anatomic ratio of oxygen to silicon in the first organic layer is greaterthan an atomic ratio of oxygen to silicon in the second organic layer.

In some embodiments, the atomic ratio of carbon to silicon in the firstorganic layer ranges from 1.20 to 1.24 and increases with decreasingdistance from the second organic layer, and the atomic ratio of carbonto silicon in the second organic layer ranges from 1.24 to 1.30. Theatomic ratio of oxygen to silicon in the first organic layer ranges from0.62 to 0.64 and increases with decreasing distance from the firstinorganic layer, and the atomic ratio of oxygen to silicon in the secondorganic layer ranges from 0.60 to 0.62.

According to some embodiments of the inventive concept, a method offabricating a display device includes preparing an organic lightemitting device, depositing an inorganic material on the organic lightemitting device to form a first inorganic encapsulation layer, formingan organic layer on the first inorganic encapsulation layer, anddepositing an inorganic material on the organic layer to form a secondinorganic encapsulation layer. Forming the organic layer includesdepositing an organic material under a first oxygen partial pressure toform a first organic layer on the first inorganic encapsulation layerand depositing an organic material under a second oxygen partialpressure that is less than the first oxygen partial pressure to form asecond organic layer on the first organic layer.

In some embodiments, forming the organic layer may further includeoxidizing the organic materials, and the organic material in forming thefirst organic layer is more actively oxidized than that in forming thesecond organic layer.

In some embodiments, the forming of the first organic layer and theforming of the second organic layer are continuous processes.

In some embodiments, the first organic layer is formed while graduallydecreasing the first oxygen partial pressure.

In some embodiments, the organic material includes alkoxysilane-basedcompounds or siloxane-based compounds.

In some embodiments, the first organic layer and the second organiclayer are formed of the same organic material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an assembled shape of a display deviceaccording to some embodiments of the inventive concept.

FIG. 1B is an exploded, perspective view of a display device accordingto some embodiments of the inventive concept.

FIG. 2 is a circuit diagram of a pixel in a display device according tosome embodiments of the inventive concept.

FIG. 3 is a vertical sectional view of a portion of a display deviceaccording to some embodiments of the inventive concept.

FIGS. 4A and 4B are vertical sectional views of a portion of anencapsulation structure in a display device of FIG. 3.

FIGS. 5A and 5B are flow charts of a process of fabricating a displaydevice, according to some embodiments of the inventive concept.

FIGS. 6A to 6F are sectional views that illustrate a process offabricating a display device, according to some embodiments of theinventive concept.

FIG. 7A is a graph of the atomic composition of a first organic layeraccording to some embodiments of the inventive concept.

FIG. 7B is a graph of the atomic composition of a second organic layeraccording to some embodiments of the inventive concept.

FIG. 8A is a graph that compares atomic ratios of oxygen to silicon infirst and second organic layers according to some embodiments of theinventive concept.

FIG. 8B is a graph that compares atomic ratios of carbon to silicon infirst and second organic layers according to some embodiments of theinventive concept.

FIG. 9A is a graph that compares atomic ratio ranges of oxygen tosilicon in first and second organic layers according to some embodimentsof the inventive concept.

FIG. 9B is a graph that compares atomic ratio ranges of carbon tosilicon in first and second organic layers according to some embodimentsof the inventive concept.

FIG. 10A is an image obtained from a surface scratch test performed on adisplay device according to some embodiments of the inventive concept.

FIG. 10B is an image obtained from a surface scratch test performed on adisplay device according to a comparative example.

DETAILED DESCRIPTION

Exemplary embodiments of the inventive concepts will now be describedmore fully with reference to the accompanying drawings, in whichexemplary embodiments are shown. Exemplary embodiments of the inventiveconcepts may, however, be embodied in many different forms and shouldnot be construed as being limited to the embodiments set forth herein.In the drawings, the thicknesses of layers and regions gray beexaggerated for clarity. Like reference numerals in the drawings maydenote like elements, and thus their description will be omitted.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. Like numbers may indicate like elements throughout.

FIG. 1A is a perspective view of an assembled shape of a display deviceaccording to some embodiments of the inventive concept. FIG. 1B is anexploded perspective view of a display device according to someembodiments of the inventive concept. FIG. 2 is a circuit diagram of apixel in a display device according to some embodiments of the inventiveconcept. Hereinafter, a display device DD according to some embodimentsof the inventive concept will be described with respect to FIGS. 1A to2.

Referring to FIGS. 1A and 1B, a display device DD according to someembodiments of the inventive concept includes a display structure DM andan encapsulation structure EN.

According to some embodiments, the display structure DM includes adisplay region DA and a non-display region NDA. The display region DAcan display an image. When viewed from a thickness direction DR3 of thedisplay device DD, the display region DA has a roughly rectangularshape, but embodiments of the inventive concept are not limited thereto.

According to some embodiments, the display region DA includes aplurality of pixel regions PA. The pixel regions PA are arranged in amatrix configuration. The pixel regions PA are defined by a pixeldefinition layer PDL (e.g., see FIG. 3). The pixel regions PA include aplurality of pixels PX (e.g., see FIG. 2). Each of the pixels PXincludes an organic light emitting device OEL (e.g., see FIG. 3).

According to some embodiments, the non-display region NDA does notdisplay an image. When viewed from the thickness direction DR3 of thedisplay device DD, the non-display region NDA surrounds and encloses thedisplay region DA. The non-display region NDA is, adjacent to thedisplay region DA in a first direction DR1 and a second direction DR2that crosses the first direction DR1.

According to some embodiments, the display structure DM includes a basestructure BS and a display layer DL disposed on the base structure BS.

According to some embodiments, the base structure BS is a substrateformed from an insulating material, such as glass, plastic, or quartz.The display layer DL includes a plurality of pixels. Each of the pixelsPX can emit light, based on electrical signals applied thereto.

Referring to FIG. 2, according to some embodiments, each of the pixelsPX is part of an interconnection structure that includes a gate line GL,a data line DAL, and a driving voltage line DVL. Each of the pixels PXincludes thin-film transistors TFT1 and TFT2, an organic light emittingdevice OEL and a capacitor Cst, which are connected to the thin-filmtransistors TFT1 and TFT2.

According to some embodiments, the gate line GL extends in the firstdirection DR1. The data line DAL extends in the second direction DR2,crossing the gate line GL. The driving voltage line DVL extends insubstantially the same direction as that of the data line DAL, i.e., inthe second direction DR2. The gate line GL transmits scan signals to thethin-film transistors TFT1 and TFT2 the data line DAL transmits datasignals to the thin-film transistors TFT1 and TFT2, and the drivingvoltage line DVL transmits a driving voltage to the thin-filmtransistors TFT1 and TFT2.

According to some embodiments, the thin-film transistors TFT1 and TFT2includes a driving thin-film transistor TFT2, which controls the organiclight emitting device OEL, and a switching thin-film transistor TFT1,which controls a switching operation of the driving thin-film transistorTFT2. As described above, each of the pixels PX includes two thin-filmtransistors TFT1 and TFT2, but embodiments of the inventive concept arenot limited thereto. For example, each of the pixels PX may include asingle thin-film transistor and a single capacitor. In certainembodiments, each of the pixels PX includes three or more thin-filmtransistors and two or more capacitors.

According to some embodiments, the switching thin-film transistor TFT1includes a first gate electrode, a first source electrode, and a firstdrain electrode. The first gate electrode is connected to the gate lineGL, and the first source electrode is connected to the data line DAL.The first drain electrode is connected to, a first common electrodethrough a contact hole. The switching thin-film transistor TFT1transmits a data signal which is applied to the data line DAL or to thedriving thin-film transistor TFT2, depending on a scan signal applied tothe gate line GL.

According to some embodiments, the organic light emitting device OELincludes a first electrode connected to the driving thin-film transistorTFT2, and a second electrode that receives a second power voltage. Theorganic light emitting device OEL includes a light-emitting patterndisposed between a first electrode and a second electrode.

According to some embodiments, the organic light emitting device OELemits light when the driving thin-film transistor TFT2 is turned-on.Color, i.e., wavelength, of light emitted from the organic lightemitting device OEL is determined depending on the kind of material usedfor the light-emitting pattern. For example, the organic light emittingdevice GEL can emit light whose color is one of red, green, blue, orwhite.

Referring back to FIGS. 1A and 1B, according to some embodiments, theencapsulation structure EN is disposed on the display structure DM. Theencapsulation structure EN covers the display layer DL. Theencapsulation structure EN protects the display layer DL againstexternal moisture or a contamination material. The encapsulationstructure EN will be described in more detail below.

FIG. 3 is a vertical sectional view of a portion of a display deviceaccording to some embodiments of the inventive concept FIGS. 4A and 4Bare vertical sectional views of a portion of an encapsulation structurein a display device of FIG. 3.

Referring to FIG. 3, according to some embodiments, a display deviceincludes the base structure BS, the display layer DL, and theencapsulation structure EN.

According to some embodiments, the base structure BS includes a baselayer SUB and a buffer layer BFL. The base layer SUB is formed of orincludes at least insulating material, such as glass, plastic, quartz,etc., but embodiments of the inventive concept are not limited thereto.The base layer SUB includes an organic polymer, such as polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polyimide, orpolyether sulfone. The material for the base layer SUB is selected basedon a desired mechanical strength, thermal stability, transparency,surface flatness, tractability, waterproofing property, etc.

According to some embodiments, a functional layer is disposed on thebase layer SUB. Although in FIG. 3 the buffer layer BFL is illustratedas the functional layer, the functional layer can include a barrierlayer. The buffer layer BFL robustly couples the base structure BS tothe display layer DL, and the barrier layer can prevent contaminationmaterial from infiltrating into the display layer DL.

According to some embodiments, the display layer DL includes a thin-filmtransistor TFT and an organic light emitting device OEL.

According to some embodiments, the thin-film transistor TFT includes adriving thin-film transistor which controls the organic light emittingdevice OEL, and a switching thin-film transistor which controls theswitching operation of the driving thin-film transistor.

According to some embodiments, the thin-film transistor TFT includes asemiconductor layer SM, a gate electrode GE, a source electrode SE, anda drain electrode DE. The semiconductor layer SM is formed of asemiconductor material and functions as an active layer of the thin-filmtransistor TFT. The semiconductor layer SM is formed from or includes atleast one of an inorganic or an organic semiconductor material.

According to some embodiments, a gate insulating layer GI is disposed onthe semiconductor layer SM. The gate insulating layer GI covers thesemiconductor layer SM. The gate insulating layer GI includes at leastone of an organic insulating material or an inorganic insulatingmaterial.

According to some embodiments, the gate electrode GE is disposed on thegate insulating layer GI. The gate electrode GE covers a region of thegate insulating layer GI that corresponds to a channel region of thesemiconductor layer SM.

According to some embodiments, the source electrode SE and the drainelectrode DE are disposed on an interlayer insulating layer IL. Thedrain electrode DE is in contact with a drain region of thesemiconductor layer SM through a contact hole that penetrates the gateinsulating layer GI and the interlayer insulating layer IL, and thesource electrode SE is in contact with a source region of thesemiconductor layer SM through a contact hole that penetrates the gateinsulating layer GI and the interlayer insulating layer IL.

According to some embodiments, a passivation layer PL is disposed on thesource electrode SE, the drain electrode DE, and the interlayerinsulating layer IL. The passivation layer PL protects the thin-filmtransistor TFT and serves as a planarization layer that provides a flattop surface.

According to some embodiments, the organic light emitting device OEL isdisposed on the passivation layer PL.

According to some embodiments, the manic light emitting device OELincludes a first electrode EL1, a second electrode EL2 disposed on thefirst electrode EL1, and an intervening layer CL disposed between thefirst electrode EL1 and the second electrode EL2.

According to some embodiments, the first electrode EL1 functions as apixel electrode or a positive terminal. The first electrode EL1 may be atransparent electrode, a transflective electrode, or a reflectiveelectrode. The first electrode EL1 is formed from or includes at leastone conductive compound that includes a metal, a metal alloy, or a metaloxide. The first electrode EL1 is formed from or includes a transparentmetal oxide, such as indium tin oxide (ITO), indium zit oxide (IZO),zinc oxide (ZnO), or indium tin zinc oxide (ITZO). The first electrodeEL1 is formed from or includes at least one of Ag, Mg, Cu, Al, Pt, Pd,Au, Ni, Nd, Ir, Cr, Li, Ca, LiF/Ca LiF/Al, Mo, Ti, compounds thereof, ormixtures thereof, such as a mixture of Ag and Mg. In certainembodiments, the first electrode EL1 has a multi-layered structure thatincludes a reflective or transflective layer formed from the abovematerials, and a transparent conductive layer formed from indium tinoxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium tinzinc oxide (ITZO).

According to some embodiments, the second electrode EL2 is used as acommon electrode or a negative-type electrode. The second electrode EL2may be a transparent electrode, a transflective electrode, or areflective electrode. The second electrode EL2 is formed from orincludes at least one conductive compound that includes a metal, a metalalloy, or a metal oxide. The second electrode EL2 is formed from orincludes a transparent metal oxide, such as indium tin oxide (ITO),indium zinc oxide (IZO), zinc oxide (ZnO) or indium tin Zinc oxide(ITZO). The second electrode EL2 is formed from or includes at least oneof Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF/Ca, LiF/Al, Mo,Ti, compounds thereof, or mixtures thereof, such as a mixture of Ag andMg. The second electrode EL2 may have a multi-layered structure thatincludes a reflective or transflective layer formed from at least one ofthe above materials, and a transparent conductive layer formed fromindium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), orindium tin zinc oxide (ITZO).

According to some embodiments, the first electrode EL1 is a reflectiveelectrode, and the second electrode EL2 is a transflective electrode ora transparent electrode. In the organic light emitting display deviceDID according to some embodiments of the inventive concept, the organiclight emitting device OEL is a top-emission type. However, embodimentsof the inventive concept are not limited thereto, and for example, theorganic light emitting device OEL may be of a bottom-emission type inother embodiments.

According to some embodiments, the pixel definition layer PDL isdisposed on the first electrode EL1 For example, the pixel definitionlayer PDL covers a portion of the first electrode EL1 and exposes otherportions of the first electrode EL1.

According to some embodiments, the pixel definition layer PDL has anopening PDL-OP. The opening PDL-OP of the pixel definition layer PDLdefines a light-emitting region.

According to son e embodiments, the intervening layer CL is disposedbetween the first electrode EL1 and the second electrode EL2. Theintervening layer CL includes a light emitting layer. The interveninglayer CL further includes a plurality of common layers, in addition tothe light emitting layer. For example, the intervening layer CL includesa hole injection layer, a bole transport layer, a light emitting layer,an electron transport layer, and an electron injection layer, which aresequentially stacked. In certain embodiments, the intervening layer CLfurther includes at least one of a hole blocking layer, a hole bufferlayer, or an electron blocking layer.

According to some embodiments, the intervening layer CL is, disposed inthe opening PDL-OP defined in the pixel definition layer PDL. Theintervening layer. CL overlaps the light-emitting region defined by theopening PDL-OP of the pixel definition layer PDL.

According to some embodiments, the encapsulation structure EN includes afirst inorganic layer IOL1, an organic layer OL disposed on the firstinorganic layer IOL1, and, a second inorganic layer IOL2 disposed on theorganic layer OL. The encapsulation structure EN is disposed on theorganic light emitting device OEL and hermetically seals the organiclight emitting device OEL.

According to some embodiments, the first inorganic layer IOL1 isdisposed on the display structure DM. The first inorganic layer IOL1 isdisposed on the organic light emitting device OEL. In detail, the firstinorganic layer IOL1 is in contact with the second electrode EL2 of theorganic light emitting device OEL. The first inorganic layer IOL1overlaps the organic light emitting device OEL and the pixel definitionlayer PDL. The first inorganic layer IOL1 is formed from or includes aninorganic material. The inorganic material includes, for example,aluminum oxide, silicon oxide, silicon oxynitride, silicon nitride, zincoxide, strontium oxide, titanium oxide, hafnium oxide, etc., butembodiments of the inventive concept are not limited thereto. The firstinorganic layer IOL1 is a barrier layer that encapsulates the organiclight emitting device OEL and prevents contamination materials frominfiltrating into the organic light emitting device OEL. Hereinafter,for convenience in description, the first inorganic layer IOL1 isreferred to as a first inorganic encapsulation layer IOL1.

According to some embodiments, the organic layer OL includes a firstorganic layer OL1 and a second organic layer OL2. The first organiclayer OL1 is disposed adjacent to the first inorganic encapsulationlayer IOL1, when viewed in a vertical section. For example, the firstorganic layer OL1 is in direct contact with the first inorganicencapsulation layer IOL1. The second organic layer OL2 is disposed onthe first organic layer OL1. The second organic layer OL2 is in directcontact with the first organic layer OL1. The second organic layer OL2is spaced apart from the first inorganic encapsulation layer IOL1 withthe first organic layer OL1 interposed therebetween. The organic layerOL has a specific thickness, allowing it to be a protection layer thatprotects the organic light emitting device OEL and as a planarizationlayer that provides a flat top surface.

According to some embodiments, the second inorganic layer IOL2 isdisposed cm the organic layer OL. The second inorganic layer IOL2 is indirect contact with the second organic layer OL2. The second inorganiclayer IOL2 overlaps the organic light emitting device OEL and the pixeldefinition layer PDL. The second inorganic layer IOL2 fully overlaps thefirst inorganic encapsulation layer IOL1 when viewed in a plan view. Thesecond inorganic layer IOL2 is formed from or includes an inorganicmaterial. The second inorganic layer IOL2 includes the same inorganicmaterial as that in the first inorganic encapsulation layer IOL1. Thesecond inorganic layer IOL2 encapsulates the organic light emittingdevice OEL and prevents contamination materials from infiltrating intothe organic light emitting device OEL. Hereinafter, for convenience indescription, the second inorganic layer IOL2 will be referred to as asecond inorganic encapsulation layer IOL2.

Referring to FIG. 4A, according to some embodiments, the organic layerOL includes the first organic layer OL1 and the second organic layerOL2. The first organic layer OL1 is disposed adjacent to the firstinorganic encapsulation layer IOL1, when viewed in a vertical section.The second organic layer OL2 is disposed on the first organic layer OL1and is spaced apart from the first inorganic encapsulation layer TOLLwhen viewed in a vertical section. The first organic layer OL1 has athickness ranging from about 500 Å to about 4000 Å.

According tip some embodiments, the organic layer OL is formed from orincludes at least one silicone-based organic compound. The organic layerOL includes an organic material that contains carbon and silicon. Theorganic layer OL includes an organic material that contains carbon,silicon, and oxygen. The organic layer OL includes a silicone-basedcompound that includes silicon-oxygen chains.

According to some embodiments, an atomic ratio of carbon to silicon inthe first organic layer OL1 differs from an atomic ratio of carbon tosilicon in the second organic layer OL2. The atomic ratio of carbon tosilicon in the first organic layer OL1 is less than the atomic ratio ofcarbon to silicon in the second organic layer OL2. The first organiclayer OL1 has a carbon content that is less than that of the secondorganic layer OL2 and has a silicon content that is greater than that ofthe second organic layer OL2.

According to some embodiments, the atomic ratio of carbon to silicon inthe first organic layer OL1 is lower than about 1.24. In detail, theatomic ratio of carbon to silicon in the first organic layer OL1 rangesfrom about 1.20 to about 1.24. The atomic ratio of carbon to silicon inthe second organic layer OL2 is greater than about 1.24. In detail, theatomic ratio of carbon to silicon in the second organic layer OL2 rangesfrom about 1.24 to about 1.30.

According to some embodiments, an atomic ratio of oxygen to silicon inthe first organic layer OL1 differs from an atomic ratio of oxygen tosilicon in the second organic layer OL2. For example, the atomic ratioof oxygen to silicon in the first organic layer OL1 is greater than theatomic ratio of oxygen to silicon in the second organic layer OL2. Thefirst organic layer OL1 has an oxygen content less than that of thesecond organic layer OL2 and has a silicon content greater than that ofthe second organic layer OL2.

According to some embodiments, the atomic ratio of oxygen to silicon inthe first organic layer OL1 is greater than about 0.62. In detail, theatomic ratio of carbon to silicon in the first organic layer OL1 rangesfrom about 0.62 to about 0.64. The atomic ratio of carbon to silicon inthe second organic layer OL2 is less than about 0.62. In more detail,the atomic ratio of carbon to silicon in the second organic layer OL2ranges from about 0.60 to about 0.62.

In some embodiments, the organic layer OL includes the first organiclayer OL1 and the second organic layer OL2. The first organic layer OL1and the second organic layer OL2 have different content ratios of carbonto silicon and oxygen to silicon. The first organic layer OL1 has alower carbon content and a higher oxygen content as compared with thesecond organic layer OL2, and thus, the first organic layer OL1 hascharacteristics similar to the first inorganic encapsulation layer IOL1,compared with the second organic layer OL2. When compared with thesecond organic layer OL2, the first organic layer OL1 may havecharacteristics similar to an inorganic layer, and thus, has goodadhesive characteristics to adhere to the first inorganic encapsulationlayer IOL1.

In some embodiments, since the organic layer OL includes the firstorganic layer OL1, which behaves like an inorganic layer and ispositioned adjacent to the first inorganic encapsulation layer IOL1,adhesive characteristics can be improved bet peen the first inorganicencapsulation layer IOL1 and the organic layer OL in the encapsulationstructure EN. This can improve stability of the encapsulation structureEN and thereby to improve reliability of the display device DD.

Referring to FIG. 4B, according to some embodiments, the organic layerOL includes the first organic layer OL1, the second organic layer OL2,and an intermediate organic layer OLC disposed between the first organiclayer OL1 and the second organic layer OL2. An atomic ratio of carbon tosilicon in the intermediate organic layer OLC has an intermediate valuebetween those in the first organic layer OL1 and the second organiclayer OL2. An atomic ratio of oxygen to silicon in the intermediateorganic layer OLC has an intermediate value between those in the firstorganic layer OL1 and the second organic layer OL2.

Referring to FIGS. 4A and 4B, according to some embodiments, contentratios of carbon and oxygen to silicon the first organic layer OL1change in a thickness direction thereof. For example, the atomic ratioof carbon to silicon in the first organic layer OL1 increases withdecreasing distance from the second organic layer OL2 and decreases withdecreasing distance from the first inorganic encapsulation layer IOL1.The atomic ratio of oxygen to silicon in the first organic layer OL1decreases with decreasing distance from the second organic layer OL2 andincreases with decreasing distance from the first inorganicencapsulation layer IOL1.

In some embodiments, the first organic layer OL1 and the second organiclayer OL2 are formed by a continuous process. Here, to realize thedifference in ratios of carbon and oxygen to silicon between the firstorganic layer OL1 and the second organic layer OL2, a process conditionchanges during the continuous process. In certain embodiments, duringthe continuous process, the intermediate organic layer OLC is formedbetween the first organic layer OL1 and the second organic layer OL2.The intermediate organic layer OLC has an intermediate content ratio ofcarbon to silicon and oxygen to silicon, when compared with the firstorganic layer OL1 and the second organic layer OL2. During a process offorming the first organic layer OL1, the process condition graduallychanges to change the ratios of carbon and oxygen to silicon in thefirst organic layer OL1 in a thickness direction thereof.

A method of fabricating a display device according to some embodimentsof the inventive concept will be described in more detail below.

FIGS. 5A and 5B are flow charts of a process of fabricating a displaydevice, according to some embodiments of the inventive concept. FIGS. 6Ato 6F are sectional views that illustrate some steps of a process offabricating a display device, according to some embodiments of theinventive concept.

A method of fabricating a display device according to some embodimentsof the inventive concept includes preparing a display structure andforming an encapsulation structure on the display structure. The displaystructure includes an organic light emitting device, and theencapsulation structure is formed to hermetically seal the organic lightemitting device.

FIG. 5A is a flow ohm of a process of forming the encapsulationstructure, according to some embodiments of the inventive concept.Forming the encapsulation structure includes forming the first inorganicencapsulation layer IOL1 (step S100), forming the organic layer OL (stepS200), and forming the second inorganic encapsulation layer IOL2 (stepS300). FIG. 5B is a flow chart of a process of forming the organiclayer, according, to some embodiments of the inventive concept. Formingthe organic layer includes depositing an organic material OM on thefirst inorganic encapsulation layer IOL1 to form the first organic layerOL1 (step 201) and then depositing the organic material OM on the firstorganic layer OL1 to form the second organic layer OL2 (step 202).

Referring to FIG. 6A, according to some embodiments, forming theencapsulation structure includes preparing the display structure DM anddepositing an inorganic material on the display structure DM to form thefirst inorganic encapsulation layer IOL1 (step S100). They, firstinorganic encapsulation layer IOL1 can be formed by a chemical vapordeposition (CVD) method, but embodiments of the inventive concept arenot limited thereto.

Referring to FIGS. 6B to 6E, forming the encapsulation structure furtherincludes forming the organic layer OL on the first inorganicencapsulation layer IOL1 (step S200). Forming the organic layer OL (stepS200) includes depositing an organic material OM on the first inorganicencapsulation layer IOL1 to form the first organic layer OL1 (step 201)and then depositing the organic material OM on the first organic layerOL1 to form the second organic layer OL2 (step 202).

According to some embodiments, the first organic layer OL1 is formed onthe first inorganic encapsulation layer IOL1 by depositing the organicmaterial OM under a first oxygen partial pressure OP1. The organicmaterial OM is formed from or includes alkoxysilane-based compounds orsiloxane-based compounds. However, embodiments of the inventive conceptare not limited thereto, and in certain embodiments, the organicmaterial OM is formed from or includes at least one ofhexamethyldisiloxane (HMDSO), tetraethyl orthosilicate (TEOS),diethoxymethylsilane (DEMS), or N-octyltrimethoxysilane (OCTMS).

According to some embodiments, forming the first organic layer OL1includes oxidizing the organic material OM under the process conditionsof the first oxygen partial pressure OP1. For example, the organicmaterial OM is decomposed by an electron beam and then oxidized underthe process conditions of the first oxygen partial pressure OP1.

According to some embodiments, the second organic layer OL2 is formed onthe first organic layer OL1 by depositing the organic material OM undera second oxygen partial pressure OP2. The second organic layer OL2 isformed in a continuous or ion-interrupted manner after the first organiclayer OL1 is formed.

According to some embodiments, the organic material OM, which is used toform the second organic layer OL2, includes alkoxysilane-based compoundsor siloxane-based compounds. The organic material OM used to form thesecond organic layer OL2 is the same as that used to from the firstorganic layer OL1. The same deposition material is used in the processesof forming the first and second organic layers OL1 and OL2, but theprocesses of forming the first and second organic layers OL1 and OL2 areperformed under different process conditions, i.e., with differentoxygen partial pressures.

According to some embodiments, the second oxygen partial pressure OP2 isless than the first oxygen partial pressure OP1. Forming the secondorganic layer OL2 includes oxidizing the organic material OM under theprocess conditions of the second oxygen partial pressure OP2. Since thesecond oxygen partial pressure OP2 is less than the first oxygen partialpressure OP1, the organic material OM more actively oxidizes during theformation of the first organic layer OL1 than during the formation ofthe second organic layer OL2. Since the organic material OM oxidizesmore actively in the formation of the first organic layer OL1, the firstorganic layer OL1 has a greater content ratio of oxygen to silicon and alower content ratio of carbon to silicon than the second organic layerOL2.

According to some embodiments, the first organic layer OL1 is formedwhile changing the first oxygen partial pressure OP1. The first organiclayer OL1 is formed while gradually decreasing the first oxygen partialpressure OP1. In this case, the first organic layer OL1 is formed tohave content ratios of carbon and oxygen to silicon that vary in athickness direction of the first organic layer OL1. In detail, theatomic ratio of carbon to silicon in the first organic layer OL1decreases with decreasing distance from the first inorganicencapsulation layer IOL1. The atomic ratio of oxygen to silicon in thefirst organic layer OL1 increases with decreasing distance from thefirst inorganic encapsulation layer IOL1.

Referring to FIG. 6F, according to some embodiments, forming theencapsulation structure includes depositing an inorganic material on theorganic layer OL to form the second inorganic encapsulation layer IOL2(step S300). The second inorganic encapsulation layer IOL2 can be formedby a chemical vapor deposition (CVD) method, but embodiments of theinventive concept are not limited thereto.

In a method of fabricating a display device according to someembodiments of the inventive concept, the second organic layer OL2 isformed in a continuous or non-interrupted manner after the first organiclayer OL1 is formed. The same deposition material are used to form thefirst and second organic layers OL1 and OL2, but the processes offorming the first and second organic layers OL1 and OL2 are performedunder different process conditions, e.g., by varying the oxygen partialpressure or voltage. In the method of fabricating a display device,since the first and second organic layers OL1 and OL2, whosecompositions differ from each other, are formed by a continuous process,the number of process steps for fabricating a display device can bereduced, thereby reducing process costs. Furthermore, stability of theencapsulation structure and reliability of a display device can beimproved.

Hereinafter, some experimental examples of embodiments of the inventiveconcept will be described in detail. Some embodiments to be describedbelow are presented to provide better understanding of the inventiveconcept, beat embodiments of the inventive concept are not limitedthereto.

FIG. 7A is a graph of the atomic composition of a first organic layeraccording to some embodiments of the inventive concept. FIG. 78 is agraph of the atomic composition of a second organic layer according tosome embodiments of the inventive concept. Data shown in FIGS. 7A and 78were measured through an X-ray photoelectron spectroscopic (XPS)analysis.

In FIGS. 7A and 7B, according to some embodiments, the x axis representsa thickness of each layer, and the y axis represents atomic percentvalues. Referring to FIGS. 7A and 7B, there was no difference incomposition between the first and second organic layers, the firstorganic layer had a relatively higher oxygen atomic percent, and thesecond organic layer had a relatively higher carbon atomic percent.

FIG. 8A is a graph that compares atomic ratios of oxygen to silicon infirst and second organic layers according to some embodiments of theinventive concept. FIG. 8B is a graph that compares atomic ratios ofcarbon to silicon in first and second organic layers according to someembodiments of the inventive concept.

Referring to FIG. 8A, the first organic layer had a higher atomic ratioof oxygen to silicon than the second organic layer. As a result of asurface oxidation, the atomic ratio of oxygen to silicon in the firstorganic layer was similar to that in the second organic layer, at arelatively shallow depth, e.g., about 100 nm, but the atomic ratio ofoxygen to silicon in the first organic layer was greater than that m thesecond organic layer, with increasing depth.

Referring to FIG. 8B, the first organic layer had a greater atomic ratioof carbon to silicon than the second organic layer.

FIG. 9A is a graph that compares atomic ratio ranges of oxygen tosilicon in first and second organic layers according to some embodimentsof the inventive concept. FIG. 9B is a graph that illustrates atomicratio ranges of carbon to silicon in first and second organic layersaccording to some embodiments of the inventive concept.

Referring to FIGS. 9A and 9B, an atomic ratio of oxygen to silicon inthe first organic layer ranges from about 0.62 to about 0.64. An atomicratio of carbon to silicon in the first organic layer ranges from about1.20 to about 1.24. An atomic ratio of oxygen to silicon in the secondorganic layer ranges from about 0.60 to about 0.62. An atomic ratio ofcarbon to silicon in the second organic layer ranges from about 1.24 toabout 1.30.

According to some embodiments of the inventive concept, since the firstand second organic layers are formed by depositing the same materialunder different process conditions, e.g., in terms of oxygen partialpressure or voltage, differences in atomic ratios of oxygen and carbonto silicon between the first and second organic layers are be large, butthe first organic layer has a higher oxygen atomic percent and a lowercarbon atomic percent, as compared with the second organic layer.

FIG. 10A is an image obtained from a surface scratch test performed onan encapsulation structure of a display device according to an exemplaryembodiment of the inventive concept, and here, the encapsulationstructure was prepared to include a first inorganic encapsulation layer,a first organic layer, a second organic layer, and a second inorganicencapsulation layer sequentially stacked in the order listed. FIG. 10Bis an image obtained from a surface scratch test performed on anencapsulation structure of a display device according to a comparativeexample, and here, the encapsulation structure was prepared to have thesame structure as that according to the inventive concept, except thatno first organic layer was provided.

Referring to FIGS. 10A and 10B, according to some embodiments, thescratch test shows that an area of a region in which surfacedelamination occurs is larger in the comparative example than in anexemplary embodiment of the inventive concept. This result shows thatthe first organic layer, which is additionally provided in a displaydevice according to an exemplary embodiment of the inventive conceptthat has a higher ratio of oxygen to silicon, can improve adhesivecharacteristics between the inorganic layer and the organic layer in theencapsulation structure, to prevent the display device from being brokenby an external scratch, thus improving stability and reliability of thedisplay device.

According to some embodiments of the inventive concept, a display devicecan effectively prevent an extraneous material, such as oxygen ormoisture, from infiltrating therein, thereby improving reliability.

According to some embodiments of the inventive concept, a method offabricating a display device includes forming layers of an encapsulationstructure through a continuous process to improve adhesivecharacteristics of the layers, which can reduce fabrication costs of adisplay device.

While exemplary embodiments of the inventive concepts have beenparticularly shown and described, it will be understood by one ofordinary skill in the art that variations in form and detail may be madetherein without departing from the spirit and scope of the attachedclaims.

What is claimed is:
 1. A method of fabricating a display device,comprising: preparing a organic light emitting device; depositing aninorganic material on the organic light emitting device to form a firstinorganic encapsulation layer; forming an organic layer on the firstinorganic encapsulation layer; and depositing an inorganic material onthe organic layer to, form a second inorganic encapsulation layer,wherein forming the organic layer comprises: depositing an organic,material under a first oxygen partial pressure to form a first organiclayer on the first inorganic encapsulation layer; and depositing anorganic material under a second oxygen partial pressure that is lessthan the first oxygen partial pressure to form a second organic layer onthe first organic layer, wherein the first organic layer has a greatercontent ratio of oxygen to silicon and a lower content ratio of carbonto silicon than the second organic layer.
 2. The method of claim 1,wherein forming the organic layer further comprises oxidizing theorganic materials, and the organic material in forming the first organiclayer is more actively oxidized than that in forming the second organiclayer.
 3. The method of claim 1, wherein the forming of the firstorganic layer and the forming of the second organic layer are continuousprocesses.
 4. The method of claim 3, wherein the first organic layer isformed while gradually decreasing the first oxygen partial pressure. 5.The method of claim 1, wherein the organic material comprisesalkoxysilane-based compounds or siloxane-based compounds.
 6. The methodof claim 5, wherein the first organic layer and the second organic layerare formed of the same organic material.